[Tupelo3]

Despite suggestions to the contrary in recent years, Alzheimer's and Parkinson's diseases do not appear to be part of a biological continuum, researchers reported.....

......"Our findings therefore imply that loci that increase the risk of both (Parkinson's and Alzheimer's) are not widespread and that the pathological overlap could instead be 'downstream' of the primary susceptibility genes that increase the risk of each disease," they concluded.

On the other hand, they cautioned that they excluded patients with Lewy body dementia, which shares characteristics of both Alzheimer's and Parkinson's, and that may have limited the power of the analysis. Also, they noted, it remains possible that future, more refined methods might yet find a common genetic basis for the disease.

http://www.medpagetoday.com/Neurology/Dementia/40832